Foundation Study On Process Of Electrosynthesis Potassium Dichromate

Potassium dichromate is an important inorganical chemical industrial product. With the development of society and technology, the consumption of potassium dichromate is increasing year-to-year in the worldwide. The study on new way of synthesis it is in full swing. Electrochemical synthesis method ,as a green technology, have many advantages sunch as good product quality, short process flow, without pollution, high selectivity of product and smooth reaction conditions . As part of national natural science foud (20676136)and "863"project(2005AA647010),this thesis carry out electrosynthesis potassium dichromate from K₂CrO₄, studied the fundamental research of optimize technological conditions , the marcokenitics and the variation law of cell voltage, which have a important science theory meaning and engineering application perspective.The experiment was carried out in a self-made two-compartment electrosynthesis reactor which consisted of anode compartment of pure titanium and cathode compartment of stainless steel. The combination anode of titanium matrix with a multiple-unit metal oxides Ti/TiO₂-RuO₂-IrO₂ coating and the cathode of stainless steel were installed in the anode chamber and the cathode chamber, respectively, and separated by the fixed Aciplex^?-F4602 fluorosulfonic acid/carboxylic acid reinforcing combination cation-exchange membrane. The interval between the electrodes was less-than 1 mm. By taking current density, reaction temperature, the initiate concentration of K₂CrO₄ and KOH , reaction time as impact factors ,the experiment was designed in order to optimize the current efficiency, percent conversion and electric energy consumption. The relatively good process conditions were fixed from analyzing results of orthogonality and significance test. The average current efficiency, average percent conversion and average electric energy consumption of 3 times repeated experiment on these conditions were 93.68% , 96.58 % and 595 kWh·t^-1.According to principle of electrochemical synthesis reaction of K₂CrO₇ from K₂CrO₄, indict that it is a complex inrreversible inhomogeneous reaction . In this article, many elementary process and its interaction and synergistic effect of electrochemical synthesis process of potassium dichromate was researched from an engineering application point of view. The kinetic data were experimentally measured at different temperatures different time and different initial K₂Cr₂O₇ concentrations of anolyte. The macro-kinetic model of the electrochemical synthesis process of K₂Cr₂O₇ was built, meanwhile, the parameters of the macro-kinetic model were established. This reaction presents a complex kinetic feature of zero order reaction. The dependence of apparent reaction rate constant k₀ on reaction temperature T is in accord with Arrhenius equation, the apparent activation energy is 7.836kJ·mol^-1.According to electrochemical reaction principle, through the cause analysis of inherent electrochemical reaction of the dependences of cell voltage on reaction time, it is pointed out that electrochemical synthesis process may be quantitatively formulated by the variation of cell voltage measured macroscopically with reaction time. So cell voltages at different reaction time were experimentally measured at different temperature and different initial anolyte concentrations C₀ in the electrochemical synthesis process of K₂Cr₂O₇. The mathematical model of variation of cell voltages with reaction time and the change rate equation of cell voltage were established. The calculated results from the model show satisfactory agreement with the experimental data, especially.